Electromagnetically actuated locking clutch for differential gears of motor vehicles

ABSTRACT

An electromagnetically actuated locking clutch for differential gears of motor vehicles having two concentrically disposed toroidal coils (8, 21) firm on a housing, one for a non-positive disk clutch (14) and the other for a positive claw clutch (26) concentrically disposed in respect thereto. Both clutches (14, 26) connect a hub (2) and a socket (3). The hub (2) and the socket (3) are each non-rotatably connected with a connecting member of the differential gear. The disk clutch (14) is closed by an automatic device when a limit value for a relative speed is exceeded. The claw clutch (26) is optionally closed and automatically opened when a limit value for an actuation period is exceeded.

The invention relates to a slip limiting device for a differential gearof a motor vehicle.

A locking clutch of this kind is known already (German Pat. No.2,920,107). A locking clutch according to German Pat. No. 2,920,107 usesfor transmitting the switching force from the annular bodies that formthe armature of the electromagnet to the two friction clutches a seriesof hydraulic intermediate members in the form of clamping bolts andactuation pistons, which are passed into guide bores and additionalcylindrical bores in the differential basket and sealed, beinginterconnected by hydraulic conduits in the differential basket. Thesealing of the clamping bolts and actuation pistons and the thermalexpansion of the oil in the hydraulic conduits give rise to seriousproblems.

The present invention is based on the problem of designing anelectromagnetically actuated locking clutch which is substantiallysimpler and operates more reliably.

This problem is solved by having the actuation members of the frictionclutch and of the armature of the electromagnet constitute a singlestructural part. There are eliminated for the transmission of theswitching force special intermediate elements which are expensive andsusceptible to failure. The invention is applicable to all differentialgears of motor vehicles, not only to axle differentials between wheelsof an axle but also to intermediate axle differentials between axles ofa motor vehicle.

A special armature can be elimiated, since the end disk additionallyassumes its function.

A special spring can be eliminated, since disks additionally assume itsfunction.

With simple, ordinary means the relative speed is limited, a fullrotation when driving and a blocking when braking are reduced and thesafety in traveling can be increased.

Control and regulation of the locking clutch can be accomplished by theuse of a microprocessor.

Added to the non-positive friction clutch can be a positive claw clutchthat operates in parallel. Thereby it is always possible to select thebetter suited of the two clutches in order to overcome the difficultiesof a particular traveling situation. When accelerating on a mountain,deficient frictional contact between wheel and ground in one or more ofthe driven wheels can occur. The claw clutch is preferred in thatsituation, since, if needed, it can makes available the whole drivingforce on the single wheel that still grips. When traveling at highspeeds on roadways that are uneven or with many curves, frictionalcontact between a wheel and the ground can repeatedly become brieflydeficient due to low or absolutely missing wheel pressure (wheelspringing, lifting of a curve inner wheel) and then becomes very goodagain. The preferred clutch in this situation is a friction clutch witha limitation of the torques and of the relative speed with thepossibility of compensating the speed, when driving in a curve, withgood frictional contact between a wheel and the ground.

Special intermediate members can be eliminated, since their functionsare additionally assumed by the structural part present, the actuationmember and the disk carrier.

Using simple, ordinary means it is possible to avoid an overloading ofdriving members, especially the drive shafts, since an alarm signaleither reminds the driver that the claw clutch is switched on or adevice causes the automatic opening of the claw clutch.

Overloading due to brisk cut-in current rush can be prevented by usingsimple ordinary means.

In the drawing is illustrated as an embodiment according to theinvention a locking clutch wherein two connecting members of adifferential gear of a motor vehicle are connected by a non-positivefriction clutch and a disk clutch and by a positive claw clutchoperating parallel therewith.

FIG. 1 is a segment of a longitudinal section.

In a housing 1 are supported two central wheels, not shown, as twoconnecting members of a differential gear, not shown. A hub 2, as afirst disk carrier 2, is firmly connected with the first connectingmember and a socket 3, as second disk carrier 3, is firmly connectedwith the second connecting member. The hub 2 carries, non-rotatably andaxially movably, limited by a guard ring 4, inner disks 5 and an enddisk 6. The socket 3 carries, non-rotatably and axially movably, limitedby the end disk 6, outer disks 7. The outer disks 7 are shaped ascorrugated disk springs 7.

A toroidal coil 8 is fastened in the housing 1. An insulating ring 9separates a magnetically conducting radially outer zone 10 from amagnetically conducting radially central zone 11 of the hub 2. Anelectric current in the toroidal coil 8 produces a magnetic flux 12 in amagnetically conducting zone 13 around the toroidal coil 8 through bothzones 10 and 11 of the hub 2, through the magnetically conducting disks5,7 and the end disk 6. The end disk 6 forms therewith at the same timean armature 6 of an electromagnet and an actuation member 6 of afriction clutch 14 of a disk clutch 14.

The hub 2 is fastened on a shaft 15. The shaft 15 carries, rotatably andaxially movably, limited by a guard ring 16, a cup spring 17 and acoupling member 18. The coupling member 18 is non-rotatably and axiallymovably connected with the socket 3. The coupling member 18 has an axialclaw 19. The hub 2 has in the zone 11 a claw section 20 fitted thereto.

In the housing 1 is fastened, radially within the toroidal coil 8, asecond toroidal coil 21. A second insulating ring 22 separates the zone11 from a magnetically conducting radially inner zone 23 of the hub 2.

An electric current in the toroidal coil 21 produces a magnetic flux 24in a magnetically conducting zone 25 around the toroidal coil 21 throughboth zones 11, 23 of the hub 2, through the shaft 15 and the couplingmember 18. The magnetic flux 24 at the same time also flows through theclaw section 19, 20 of the coupling member 18 and of the hub 2. Thecoupling member 18 thus simultaneously forms an armature 18 of anelectromagnet and an actuation member 18 of a claw clutch 26.

A restoring force of a spring 7, constituted by the outer disks 7 shapedas corrugated disk springs 7, opens and an electric current in atoroidal coil 8 closes, a non-positive friction clutch 14, a disk clutch14.

A restoring force of a spring 17, constituted by the cup spring 17,opens, and an electric current in a toroidal coil 21 closes a positiveclaw clutch 26.

Devices for optional actuation and control and regulation of bothclutches 14, 26 are not shown, since they are known and common. To thembelong speed sensors for the speeds of both connecting members, inputmembers and data memory for optional input and storage of limit valuesfor a relative speed and an actuation cycle, a clock unit, amicroprocessor with a differential picture for determining a relativespeed from both speeds with a comparator for comparing the relativespeed with a limit value and for forming an alarm signal to control anelectric current for closing the friction clutch 14 with a time counterfor forming an actuation cycle of the claw clutch 26, with a comparatorfor comparing the actuation time of a limit value and for forming analarm signal for warning the driver and/or disconnecting an electriccurrent and thus opening the claw clutch 26.

REFERENCE NUMERALS

1: housing

2: hub, disk carrier

3: socket, disk carrier

4: guard ring

5: inner disk, disk

6: end disk, actuation member, armature

7: outer disk, disk, corrugated disk spring, spring

8: toroidal coil

9: insulating ring

10: zone

11: zone

12: magnetic flux

13: zone

14: friction clutch, disk clutch, clutch

15: shaft

16: guard ring

17: cup spring, spring

18: coupling member, actuation member, armature

19: drag section

20: drag section

21: toroidal coil

22: insulating ring

23: zone

24: magnetic flux

25: zone

26: claw clutch, clutch.

We claim:
 1. An electromagnetically actuated sliplimiting clutch for the differential gear of a motor vehicle including the following features:a first torque-transmitting connecting member of the differential gear non-rotationally supporting inner disks, a second connecting member non-rotationally supporting outer disks, said inner and outer disks comprising a sliplimiting friction clutch for said differential gear, a first toroidal coil fastened to a housing and interacting with a rotatable annular first armature closing said sliplimiting friction clutch,characterized by said first connecting member non-rotationally supported a first claw section (20), said second connecting member non-rotationally supporting a second claw section (19), said claw sections (19, 20) form a sliplimiting claw clutch (26) for said differential gear, a second toroidal coil (21) fastened to the housing and interacting with a rotatable annular second armature (18) closing said sliplimiting claw clutch (26), a spring (17) opening said sliplimiting claw clutch (26), wherein said first and second toroidal coils are alternatively independently energized to alternatively engage said friction clutch or said claw clutch.
 2. A sliplimiting clutch according to claim 1, characterized by the following features:said inner disks (5) have flat rubbing surfaces, said first armature (6) is an end disk for said inner disks (5), said outer disks (7) also have substantially flat rubbing surfaces, but are shaped as corrugated disk springs and open said sliplimiting friction clutch (14), and said second armature (18) supports said second claw section (19).
 3. A sliplimiting clutch according to claim 1, characterized by the following features:a hub (2) is firmly connected with said first connecting member via a shaft (15), said hub (2) non-rotationally supports said inner disks (5, 6) and said first claw section (20), a disk carrier (3) is firmly connected with said second connecting member, said disk carrier (3) non-rotationally suports said outer disks (7) and said second armature (18), and said second armature (18) supports said second synchronization section (19).
 4. A sliplimiting clutch according to claim 1, characterized by the following features:a first insulating ring (9) magnetically separates a magnetically conductive radially outer zone (10) of a hub (2) from a radially central zone (11) of said hub (2) and mechanically connects both zones together, a second insulating ring (22) magnetically separates said central zone (11) from a radially inner zone (23) of said hub (2) and mechanically connects both zones together, an electric current in said first toroidal coil (8) produces a first magnetic flux (12) for said sliplimiting friction clutch (14), an electric current in said second toroidal coil (21) produces a second magnetic flux (24) for said sliplimiting claw clutch (26), said central zone (11) of said hub (2) conducts said first magnetic flux (12) and said second magnetic flux (24), said central zone (11) of said hub (2) non-rotationally supports said inner disks (5, 6) of said sliplimiting friction clutch (14) and said first claw section (20).
 5. A sliplimiting device for a differential gear of a motor vehicle, which comprises:a differential gear transmitting power from an input member to first and second output members, a friction clutch 14 non-positively connecting the two output members of the differential gear and thus limiting a speed difference between them, a claw clutch 26 positively connecting the two output members of the differential gear and thus eliminating speed difference between them, a first electromagnet engaging the friction clutch 14, a second electromagnet engaging the claw clutch 26, wherein said first and second electromagnets are alternatively independently energized to alternatively engage said friction clutch or said claw clutch.
 6. The sliplimiting device of claim 5 further including a logic device that controls an electric current in a magnet coil 8 of the first electromagnet, and thus controlling the friction clutch 14 and limiting a speed difference between the two output members of the differential gear.
 7. A sliplimiting device of claim 5 further includinga logic device that interrupts electric current in a magnet coil 21 of the second electromagnet after a preset time thereby disengaging the claw clutch 26; and said logic device prevents electric current in the magnet coil 21 if a speed difference between the two output members of the differential gear exceeds a preset threshold and thus prevents the claw clutch 26 from being engaged.
 8. A sliplimiting device of claim 5 which includes the following features:each of the two electromagnets has a magnet coil 8, 21 in a coil case fixed to said housing 1 of the differential gear; said housing 1 supports a rotatable shaft 15 and a rotatable shell 3; said shaft 15 and said shell 3 are each non-rotatably connected to one of three members of the differential gear; the friction clutch 14 is a multiple disk clutch with inner disks 5 on an inner disk carrier, with outer disks 7 in an outer disk carrier, and with an end disk 6 which forms a first armature of the first electromagnet; said outer disks 7 are shaped as corrugated disk springs which disengage said friction clutch 14; an electric current in the magnet coil 8 of the first electromagnet produces a first magnetic flux 12 around the magnet coil 8 through an outer section 13 of the coil case, through an intermediate section 11 of a hub 2, through all disks 5, 6, 7 and through an outer section 10 of the hub 2 back to the outer section 13 of the coil case, and thus the first electromagnet engages the friction clutch 14; an inner section 23 of said hub 2 is fixed to said shaft 15; an outer insulating zone 9 magnetically separates and mechanically connects the outer section 10 with said intermediate setion 11 of said hub 2; an inner insulating zone 22 magnetically separates and mechanically connects the inner section 23 with said intermediate section 11 of said hub 2; said shell 3 forms the outer disk carrier of the friction clutch 14, said intermediate section 11 of said hub 2 forms an inner disk carrier of said friction clutch 14 and a first claw section 20 of a claw clutch 26; an axially movable second armature 18 of the second electromagnet is non-rotatably connected with said shell 3, is rotatably supported on said shaft 15, and forms a second section 19 of said claw clutch 26; a cup spring 17 axially between said hub 2 and the second armature 18 presses said second armature 18 against a guard ring 16 on said shaft 15, and thus disengages said claw clutch 26; and an electric current in the magnet coil 21 of the second electromagnet produces a second magnetic flux 24 around the second magnet coil 21 through an inner section 25 of the coil case, through said intermediate section 11 of said hub 2, through the two claws sections 19, 20, through said second armature 18, through said shaft 15 and through said inner section 23 of said hub 2 back to said inner section 25 of the coil case, and thus the second electromagnet engages said claw clutch
 26. 